Personal portable devices can perform a communication by constructing low-rate wireless personal area networks (hereinafter abbreviate LR-WPAN).
As an example of the LR-WPAN, there is a network following IEEE 802.15.4 standard. IEEE 802.15.4 standard provides transmission speed of 20 Kbps and 40 Kbps in 868/915 MHz band using BPSK (binary phase-shift keying) and provides the transmission speed of 250 Kbps in 2.45 GHz band using O-QPSK (offset quadrature phase-shift keying). IEEE 802.15.4b standard provides transmission speed of 250 Kbps in 868/915 MHz band using the O-QPSK as well.
An MBAN (medical body area network) system, which is one of the networks following IEEE 802.15.4 standard, is designed to provide a flexible platform for supporting a wireless networking of a plurality of sensors used to monitor physiological data of a patient in such a healthcare facility as a hospital.
The MBAN system operates in 2360 MHz˜2400 MHz bands based on IEEE 802.15.4j and a maximum emission bandwidth of the MBAN system is limited to 5 MHz.
In case of operating in 2360˜2390 MHz, a transmit power of the MBAN system corresponds to a smaller value among 1 mW and 10*log(B) dBm. In this case, B corresponds to 20 dB emission bandwidth. In case of operating in 2390˜2400 MHz, the transmit power of the MBAN system corresponds to a smaller value among 20 mW and 10*log(B) dBm. In this case, B corresponds to 20 dB emission bandwidth.
2360˜2400 MHz band is a frequency band already assigned to a different wireless communication system. The MBAN system operates based on a radio cognitive technology. The radio cognitive technology means a communication technology performed by adaptively changing such a transmission/reception property as a frequency band, transmit power, a coding scheme, and the like in a manner that a network or a radio communication device actively detects and judges a surrounding communication environment for an optimized communication. In this case, if a radio cognitive device detects a use of a different licensed user (primary user) in a frequency band of which the radio cognitive device intends to use, to operate in a manner of not interfering the communication of corresponding users is the first priority.
To this end, in case of operating in 2360˜2390 band, the MBAN devices should operate in an indoor of a registered healthcare facility. In particular, a use of 2360˜2390 MHz band should be controlled by a cooperation with the different licensed user. If the different licensed user uses the corresponding band, all operations in the corresponding band are initialized and should be resumed by newly using 2390˜2400 MHz band. In some cases, operations can be resumed not by using 2390˜2400 MHz band but by moving to a different channel in 2360˜2390 MHz.
If the MBAN devices move to an outdoor, the MBAN devices stop operating or should transmit in a manner of changing a transmission band to 2390˜2400 MHz, which is used as a basic band. In case of operating in 2390˜2400 MHz band, the MBAN devices can be used irrespective of whether the MBAN devices are positioned at the indoor or the outdoor.
In a legacy MBAN system, in case that the aforementioned specific situation occurs, a method of switching a channel used in a prescribed band among 2360˜2390 MHz band and 2390˜2400 MHz band to a channel of a different band is not defined yet.